In recent years, there has been a steadily increasing interest in the use of composite materials in the aircraft industry. In particular, much effort has been directed toward developing technology for producing and using components made from conductive plastics, such as graphite-reinforced composites. There are a number of situations in which it is desirable to plate a component made from such a composite material. These situations include those in which electronic structures are to be housed inside the composite component and in which it is necessary to protect the electronic structures from electromagnetic intereference and electromagnetic pulses. Other situations in which there is a need for plating a composite component include those situations in which it is desired to ground the component and those situations in which it is desired to provide protection for the component against corrosion or abrasion.
Known methods for applying plating to plastics require immersing the component into a tank of plating solution. Such methods are unsuitable for components that are too large to be immersed and for many components that are assemblies. Immersion of assembly components is generally not acceptable since the solutions tend to collect and remain in the spaces between the parts of the assembly. This can cause corrosion of the parts and could also possibly interfere with the functioning of the component and surrounding components. Immersion of conductive plastic components is also relatively expensive to carry out and requires large quantities of plating solution.
Another problem associated with plating conductive plastics is that it is necessary to use very low current densities to get the process started and lay down the initial layer of plating. The current density must be kept at a very low level because higher current densities would tend to overheat the plastics and thereby damage them. The need to use very low current densities makes the application of conventional brush plating techniques using conventional acid plating solutions impractical if not impossible. At the low current densities required, the acid in the plating solutions consumes the plated copper as rapidly as it is plated. Attempts to speed up the process result in poor adhesion of the plate to the component.